In the powdered materials industry, there has become an increased interest in purer and purer powders. There are a variety of reasons for this interest. In the semiconductor industry, and more specifically the hard disk industry, there is a need for purer and purer metals. Components such as ¾″ inch hard drives in cell phones and MP3 players can have up to six layers of metal on the mini-hard drives in order to achieve the storage capacity needed for video and other data. One of the metals that is used for coating is ruthenium. Here, the oxygen content is critical. If the oxygen content is too high, it can result in the formation of ruthenium-oxides, which are non-conductive. Non-conductivity poses problems when trying to store data.
FIG. 1 illustrates one example of powder particles 100 that are typically used in the materials industry. These powder particles 100 typically contain impurities, such as oxygen content 102 disposed around their core. The industry is looking for purification levels equal to or less than 200 ppm of oxygen in the starting powders. Currently, one attempted solution is to place the powder in a vacuum furnace or in a hydrogen-fired vacuum furnace on a tray. The furnace is brought up to relatively high temperatures. The oxygen content (and moisture) is desorbed from the powder. Hydrogen can flow over the powder to grab and remove the oxygen and moisture content, which is pumped out, leaving a purer powder.
The downside of these furnace technologies is that they require the use of high temperatures for a long period of time. One problem with this requirement is that it places a limitation on the minimum size of grain that can be purified. The smaller the grain size, the lower the sintering temperature is for the powder, thus making small grain powders difficult to purify using these technologies. What is needed is a more cost effective technology that allows relatively small grains to be purified without sintering.
These issues are important to the powder industry in general. Cutting tools can be formed from powders, such as tungsten-carbide, tungsten-nitride and the like. However, the powders often contain oxygen, sometimes in the form of thin oxygen layers formed around each particle. In sintering the powders together to form the cutting tools, it is desirable to maintain the powder-like nature. However, it is important to minimize the void between the particles. If the void is too big, the structural integrity of the end product suffers. If there is too much oxygen, the particles will not sufficiently sinter together. When using a cutting tool made from powders having these deficiencies, the lack of structural integrity can cause the tool to fracture. What is needed is a better way to take oxygen out of powders, reduce the voids, and prepare the powders for sintering.
FIG. 2 illustrates one system 200 that has be used to try and purify powders. Here, the target powder 240 (for example, boron) is disposed in a crucible 230 that is housed within a microwave production chamber 210, such as a microwave oven. Hydrogen gas flows from a gas supply system 220 into the microwave production chamber 210 via a conduit or tube 225. As the hydrogen gas flows into the microwave production chamber 210 and the crucible 230, the microwave production chamber 210 generates and applies microwaves to the hydrogen gas, thereby forming a plasma 250 and creating hydrogen radicals, which flow over the target powder 240 and are drawn out of the chamber 210 along with oxygen content from the target powder. This drawing force is supplied by a vacuum pump 260. Although this system removes a portion of the oxygen content, there is a problem with having the target powder being exposed to the energy of the microwaves. In this configuration, the target powder can loosely couple to the microwave and heat up. This parasitic heating can result in the powder being crystallized. In circumstances where amorphous powders are preferred, this crystallization is highly undesirable.
Therefore, what is needed in the art is an efficient and cost effective system and method of removing oxygen content from a target powder, while avoiding or minimizing any parasitic heating.